The present invention relates to a waterproof connector, particularly to a waterproof connector in which conductive members such as contacts and a shell are formed integrally with a housing.
In recent years, there is a strong demand for waterproof function in various electronic devices and accordingly, waterproof connectors having waterproof properties have been under development as connectors for establishing connections with external devices.
One example of such waterproof connectors is a connector in which conductive members such as contacts and a shell are formed inside a housing made of an insulating resin to be integral with the housing by, for example, insert molding. Owing to the integral molding, surfaces of the conductive members tightly adhere to the insulating resin at portions embedded in the housing because of a shrinking force of the insulating resin, and water is prevented from penetrating from the outside to the inside of the connector through boundary portions between the housing and the conductive members.
In general, however, a metal material making up the conductive members, such as contacts and a shell, and a resin material making up the housing are different in thermal expansion coefficient from each other, and therefore, when, for example, the connector is exposed to a high temperature environment during a soldering process such as reflow mounting in mounting the connector onto a circuit board of an electronic device, due to the different degree of expansion between the conductive members and the insulating resin, the insulating resin tightly adhering to surfaces of the conductive members may be separated therefrom. Once separated, the surfaces of the conductive members and the insulating resin are to have gaps therebetween, and water may disadvantageously enter the inside of the connector through the gaps even after the temperature falls to ambient temperature.
Aside from that, in a fitting process of a counter connector with the connector, the counter connector may be forcibly fitted in a direction oblique to the fitting axis, which is so-called “ill fitting,” and a high stress may be applied between the housing and the conductive members. In this case, again, the insulating resin of the housing may be separated from the surfaces of the conductive members, thereby damaging waterproof properties of the connector.
To cope with it, a waterproof connector in which a waterproof shaped section composed of grooves or protrusions is formed at the portion of a surface of a conductive member to be embedded in a housing to thereby improve waterproof properties, was filed by the present applicant and has been registered (JP 5433776 B).
In the waterproof connector of JP 5433776 B, for instance, as shown in FIG. 15A, a plurality of grooves 3 are formed in a surface of a fixed section of a conductive member 2 embedded and fixed in a housing 1 made of an insulating resin, so as to surround and enclose the periphery of the conductive member 2.
Owing to the grooves 3, even if the insulating resin constituting the housing 1 is separated from the surface of the conductive member 2 due to the difference between the thermal expansion coefficients of an insulating resin material and a metal material or due to so-called ill fitting, and water penetrates along the interface between the housing 1 and the conductive member 2, the penetrating water is blocked by the grooves 3.
Meanwhile, in recent years, as downsizing and densification of electric devices progress, a small connector is required, and use of a thin housing is desired accordingly. To minimize the decrease in strength of a connector caused by a thinner housing, for instance, JP 7-207151 A proposes a resin composition for connectors with higher shock resistance and heat resistance as obtained by mixing a resin material with an inorganic reinforcing material.
When, however, the housing 1 in the waterproof connector of JP 5433776 B is formed from the resin composition for connectors described in JP 7-207151 A in order to enhance both waterproof properties and strength, if an inorganic reinforcing material 4 contained in the resin composition for connectors enters the insides of the grooves 3 of the conductive member 2 as shown in FIG. 15B, the contact area between the resin material and the inner surfaces of the grooves 3 is reduced, resulting in the decrease in adhesion between the housing 1 and the grooves 3 of the conductive member 2. Thus, the decrease in adhesion of the housing 1 to the grooves 3 of the conductive member 2 may lead to lower waterproof properties of the connector.